Not attaching plugins with serverless-http

[pselle]

User reported difficulty in using serverless plugin + adding iopipe logger plugin.

Steps to reproduce the issue:

1. Have express app using serverless-http library
2. Configure IOpipe with serverless plugin
3. update package.json to configure plugins to add logger plugin

Describe the results you received:

Library does not have plugins available

Describe the results you expected:

Plugins to work

[mskutin]

Refer to this gist https://gist.github.com/mskutin/17aa9db06c5257515dd84697820a7386